Predation On Native Anurans By Invasive Vertebrates In The Atlantic Rain Forest, Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)203 Specia lissue7074161812/2011-2, CNPq, Conselho Nacional de Desenvolvimento Científico e Tecnológico303776/ 2015-3, CNPq, Conselho Nacional de Desenvolvimento Científico e Tecnológico3855/13-9, CAPES, Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Tunneling conductance in strained graphene-based superconductor: Effect of asymmetric Weyl-Dirac fermions

Based on the BTK theory, we investigate the tunneling conductance in a uniaxially strained graphene-based normal metal (NG)/ barrier (I)/superconductor (SG) junctions. In the present model, we assume that depositing the conventional superconductor on the top of the uniaxially strained graphene, normal graphene may turn to superconducting graphene with the Cooper pairs formed by the asymmetric Weyl-Dirac electrons, the massless fermions with direction-dependent velocity. The highly asymmetrical velocity, vy/vx>>1, may be created by strain in the zigzag direction near the transition point between gapless and gapped graphene. In the case of the highly asymmetrical velocity, we find that the Andreev reflection strongly depends on the direction and the current perpendicular to the direction of strain can flow in the junction as if there was no barrier. Also, the current parallel to the direction of strain anomalously oscillates as a function of the gate voltage with very high frequency. Our predicted result is found as quite different from the feature of the quasiparticle tunneling in the unstrained graphene-based NG/I/SG conventional junction. This is because of the presence of the direction-dependent-velocity quasiparticles in the highly strained graphene system.Comment: 18 pages, 7 Figures; Eq.13 and 14 are correcte

Models of electron transport in single layer graphene

The main features of the conductivity of doped single layer graphene are analyzed, and models for different scattering mechanisms are presented.Comment: 15 pages. Submitted to the Proceedings of the ULTI symposium on Quantum Phenomena and Devices at Low Temperatures, Espoo, Finland, to be published in the Journ. of Low. Temp. Phy

Exact eigenstate analysis of finite-frequency conductivity in graphene

We employ the exact eigenstate basis formalism to study electrical conductivity in graphene, in the presence of short-range diagonal disorder and inter-valley scattering. We find that for disorder strength, $W \ge$ 5, the density of states is flat. We, then, make connection, using the MRG approach, with the work of Abrahams \textit{et al.} and find a very good agreement for disorder strength, $W$ = 5. For low disorder strength, $W$ = 2, we plot the energy-resolved current matrix elements squared for different locations of the Fermi energy from the band centre. We find that the states close to the band centre are more extended and falls of nearly as $1/E_l^{2}$ as we move away from the band centre. Further studies of current matrix elements versus disorder strength suggests a cross-over from weakly localized to a very weakly localized system. We calculate conductivity using Kubo Greenwood formula and show that, for low disorder strength, conductivity is in a good qualitative agreement with the experiments, even for the on-site disorder. The intensity plots of the eigenstates also reveal clear signatures of puddle formation for very small carrier concentration. We also make comparison with square lattice and find that graphene is more easily localized when subject to disorder.Comment: 11 pages,15 figure

Temperature-responsive nanomagnetic logic gates for cellular hyperthermia

While a continuous monitoring of temperature at the micro- and nano-scales is clearly of interest in many contexts, in many others a yes or no answer to the question "did the system locally exceed a certain temperature threshold?" can be more accurate and useful. This is the case of hard-to-detect events, such as those where temperature fluctuations above a defined threshold are shorter than the typical integration time of micro/nanothermometers and systems where fluctuations are rare events in a wide time frame. Herein we present the synthesis of iron selenide magnetic nanoplatelets and their use as non-volatile logic gates recording the near infrared (NIR) dose that triggers a temperature increase above a critical temperature around 42 °C in prostate cancer cell cultures. This use is based on the bistable behavior shown by the nanoplatelets below a magnetic phase transition at a tunable temperature T C and on their photothermal response under NIR light. The obtained results indicate that the synthesized nanomagnets may be employed in the future as both local heaters and temperature monitoring tools in a wide range of contexts involving systems which, as cells, are temperature-sensitive around the tunable T C

RAG Recombinase as a Selective Pressure for Genome Evolution

The RAG recombinase is a domesticated transposable element co-opted in jawed vertebrates to drive the process of the so-called V(D)J recombination, which is the hallmark of the adaptive immune system to produce antigen receptors. RAG targets, namely, the Recombination Signal Sequences (RSS), are rather long and degenerated sequences, which highlights the ability of the recombinase to interact with a wide range of target sequences, including outside of antigen receptor loci. The recognition of such cryptic targets by the recombinase threatens genome integrity by promoting aberrant DNA recombination, as observed in lymphoid malignancies. Genomes evolution resulting from RAG acquisition is an ongoing discussion, in particular regarding the counter-selection of sequences resembling the RSS and the modifications of epigenetic regulation at these potential cryptic sites. Here, we describe a new bioinformatics tool to map potential RAG targets in all jawed vertebrates. We show that our REcombination Classifier (REC) outperforms the currently available tool and is suitable for full genomes scans from species other than human and mouse. Using the REC, we document a reduction in density of potential RAG targets at the transcription start sites of genes co-expressed with the rag genes and marked with high levels of the trimethylation of the lysine 4 of the histone 3 (H3K4me3), which correlates with the retention of functional RAG activity after the horizontal transfer.Instituto Gulbenkian de Ciência; Optimus alive award; Fundação para a Ciência e Tecnologia grant: (SFRH/BPD/65292/2009).info:eu-repo/semantics/publishedVersio

Adatoms in Graphene

We review the problem of adatoms in graphene under two complementary points of view, scattering theory and strong correlations. We show that in both cases impurity atoms on the graphene surface present effects that are absent in the physics of impurities in ordinary metals. We discuss how to observe these unusual effects with standard experimental probes such as scanning tunneling microscopes, and spin susceptibility.Comment: For the Proceedings of the "Graphene Week 2008" at the ICTP in Trieste, Italy. 8 pages, 8 figure

Sugar bislactones by one-step oxidative dimerisation with pyridinium chlorochromate versus regioselective oxidation of vicinal diols

Synthesis of 10-membered bislactones by PCC oxidation of methyl 2,6-di-O-pivaloyl-α-D-glucopyranoside and methyl 4,6-O-benzylidene-α-D-glucopyranoside is described, with emphasis on their structure elucidation using the information gained by combination of NMR spectroscopic techniques with X-ray diffraction data. In alternative, the use of PCC and PCC adsorbed on silica gel or alumina for the regioselective oxidation of vicinal diols in sugars is also reported. Both bislactones showed antifungal activity against Candida albicans, and were slightly active against the bacteria Bacillus subtilis. The bislactone presenting pivaloyl protecting groups also promoted some growth inhibition of Staphylococcus aureus.info:eu-repo/semantics/publishedVersio

A universal Hamiltonian for the motion and the merging of Dirac cones in a two-dimensional crystal

We propose a simple Hamiltonian to describe the motion and the merging of Dirac points in the electronic spectrum of two-dimensional electrons. This merging is a topological transition which separates a semi-metallic phase with two Dirac cones from an insulating phase with a gap. We calculate the density of states and the specific heat. The spectrum in a magnetic field B is related to the resolution of a Schrodinger equation in a double well potential. They obey the general scaling law e_n \propto B^{2/3} f_n(Delta /B^{2/3}. They evolve continuously from a sqrt{n B} to a linear (n+1/2)B dependence, with a [(n+1/2)B]^{2/3} dependence at the transition. The spectrum in the vicinity of the topological transition is very well described by a semiclassical quantization rule. This model describes continuously the coupling between valleys associated with the two Dirac points, when approaching the transition. It is applied to the tight-binding model of graphene and its generalization when one hopping parameter is varied. It remarkably reproduces the low field part of the Rammal-Hofstadter spectrum for the honeycomb lattice.Comment: 18 pages, 15 figure